Rubber-to-metal bonding adhesives are commonly used in applications where a robust, rubber-tearing bond, is required between a rubber and metal substrate. In current processes, solvent or aqueous based adhesives are applied to the metal. Often a primer is employed along with a topcoat adhesive, wherein the primer is applied first to the metal, dried, then an adhesive is applied atop the primer. These primer/adhesive combinations are designed to chemically react with the metal, the rubber, and each other to form a chemical and mechanical bond between the substrates. Most commonly, the rubber/metal bond is formed during the vulcanization process in which heat and pressure are applied to the assembly.
In the current process common in the industry, the metal surface is cleaned, primed, and then the bonding agents are applied in a process similar to painting with a spray gun or a roller. When priming and applying the adhesive much more time is required to allow the primer and solvents to dry or “set up” to the point where rubber can be applied. Also, because of the hazards of the primers and solvents, strict handling procedures and heavy environmental regulations are in place to protect the employees and the surrounding environment, respectively.
An additional disadvantage of these bonding systems is the aqueous or solvent carrier itself. With a non-volatile content commonly in the range of 10-30%, the majority of the “product” is merely the carrier medium which is driven off prior to bonding. Thus, a substantial portion of the cost associated with shipping product from the manufacturer to a user is that associated with the non-reactive, i.e. non-participating in bonding, aspects of the product. Additionally, there are additional process steps associated with traditional adhesives including ensuring adequate mixing of product prior to application, and drying time associated with awaiting evaporation of the carrier fluid from the applied adhesive.